Digital cameras have been reduced in size and weight in recent years with the objective of improving portability. Higher performance is being sought while keeping the size of the image sensing device and the diameters of lenses small in order to attain the objective. In particular, slimmer design has been achieved by a method of bending the optic axis using a dioptric member that employs a reflecting mirror or a prism in the optical system, and by projecting part of the optical system from within the camera body when a picture is to be taken and retracting it into the camera body when a picture is not to be taken. (For example, see the specifications of Japanese Patent Application Laid-Open Nos. 10-142671 and 2004-20849).
However, it is known that regardless of whether the optical system adopted is the one that uses the dioptric member or the one that is partially projected at the time of photography, limitations are imposed upon the angle of view that allows picture taking and upon the size of the image sensing device relative to the thickness of the camera body in order to satisfy the requirements of slimmer design and higher performance.
An example of a slim-body camera in which the picture-taking optical system is provided with a reflecting optical member formed to have a curved surface to make possible wide-angle image sensing and telephoto image sensing is disclosed in the specification of Japanese Patent Application Laid-Open No. 7-333505.
Further, an example of a slim-body camera that illustrates the relationship between the thickness of a curved optical system accommodated in the camera body and the size of the image formed is disclosed in the specification of Japanese Patent Application Laid-Open No. 2000-515255.
Japanese Patent Application Laid-Open No. 7-333505 contemplates a reduction in thickness and weight by providing the camera with a function that corresponds to the front lens group of the image sensing lenses. This is achieved by providing the reflecting optical member with a curved surface. Although wide-angle image sensing is possible in a case where the shape of the curved surface of the reflecting optical member is convex, this arrangement is not suited to telephoto image sensing. In other words, the shape of the curved surface is required to be concave in order to perform telephoto image sensing, and the problem is that this method using the concave surface does not make it possible to satisfy the wide-angle and telephoto angle of view requirements simultaneously. Although a method of electrically controlling the shape of the curved surface of the reflecting optical member is conceivable, there are limitations upon the shape that can be varied and an additional problem is that circuit devices for control, etc., are required.
Further, Japanese Patent Application Laid-Open No. 2000-515255 aims to reduce the thickness of the camera body while providing the front lens group of the image sensing lenses with an image sensing lens that does not project from the camera body. However, a problem which arises is that owing to the relationship between the thickness of the optical system and the size of the image formed, the thickness of the camera body becomes thicker as the size of the image sensing device becomes larger.